Cash Pots are common on fruit machines and whilst some fruit machines do not have any cash pot others have one and some have more 3 being fairly common place.
Most cash pots are progressive meaning their value is not fixed and rises as players wager more on the machine, one common strategy is to wait until the cash pots are high on a machine before playing that way when they do pay out you know you have a chance of winning a larger amount.
Most but not all Fruit Machines have a Cash Pot feature. This is a seperate prize that is shown during the Bonus Trail feature that shows the progress of your cash prizes. There is sometimes a multiplier that can be won during the Bonus Trail that would multiply what you have accumulated in the cash pot.
As the maximum payout of land based fruit machines is governed by law so too is the way that the cash pot amount is shown to increase. For example a fruit machine is not allowed to appear to show the cash pot increasing faster at after a large amount of play as compared to when it is first being played on. It should be noted neither this or the maximum jackpot law apply to online fruit machines.